I have an ebook which I converted successfully with Calibre 5.5 from HTML/CSS to mobi and have uploaded it to MobileRead - War is a Racket by Butler, Smedley D if it makes any difference.

The Title Page of the book has this HTML
<div id="titlepage">
<h1>War is a Racket</h1>
<h3>by</h3>
<h2>Maj.General Smedley D. Butler</h2>
<div class="photoholder">
<img src="SmedleyButler.jpg"
alt="Smedley Butler" width="300" height="376"/>
</div> <!-- End of photoholder div -->
</div> <!-- End of Title page div; page break in CSS -->

With the conversion using Calibre 5.5 all that fits nicely on one page of my Cybook.

But when I tried to convert the same HTML/CSS with Calibre 6.2 the page is broken after the 'by' so that 'War is a Racket' and 'by' are centred on one page and 'Maj.General Smedley D Butler' and the graphic are on the next page. This is not what I want.

I suspect that it has something to do with the Structure Detection section of the conversion section. I did not make any changes to the defaults on either conversion; I relied on the setup in the HTML/CSS to define the structure and pagination.

So two questions:
If it is the Structure Detection options which has caused the difference how to I turn this section off, or not use it? If not, what has caused the difference?
Why have this section at all? I've taken some pains to set up the structure of the book in the HTML/CSS; why require that I set it up in Calibre instead or as well?